1. Field of the Invention
The present invention relates to a magnetoresistive head comprising a magnetoresistive element to detect a magnetic field from a magnetic recording medium.
2. Description of Related Art
The magnetoresistive head (will be referred to as "MR head" hereinunder) using a magnetoresistive element (will be referred to as "MR element" hereinunder) to detect a magnetic field from a magnetic recording medium has been proved to have a problem that the MR element is broken down due to an electrostatic discharge (ESD) or electrical overstress (EOS), resulting in a deterioration of the MR head.
More particularly, an ESD or EOS causes an overcurrent which will flow to an MR element which will thus be damaged by a heat and magnetic field developed by the overcurrent.
It is considered that through a series of processes such as wafer forming, working, assembling, etc. to produce an MR head, an external electric charge flows into the MR head under production through the processes and causes an overcurrent to flow to an MR element of the MR head, the overcurrent causing to develop a heat and magnetic field which will damage the MR element directly or indirectly.
Note that in the wafer forming process, head elements forming together an MR head are formed on a wafer substrate. The working process is such that the wafer substrate on which the MR head elements have been formed is cut into individual MR head pieces and the MR head pieces are machined in a predetermined manner. In the assembling process, the MR head thus machined is mounted on a head base and terminals of the MR head are connected to predetermined wires, to thereby assemble a magnetic head unit comprising the MR head.
Further to the above consideration, the MR element is broken down in some cases due to ESD/EOS also after assembling the MR head in the magnetic head unit. More specifically, when the MR head is assembled in a hard disc drive, for example, an electric charge flows into the MR head from a magnetic disc, causing an overcurrent to flow to an ME element of the MR head, as the case may be. Such an overcurrent also will damage the MR element.
To prevent the MR element from being broken down due to ESD/EOS, it has been proposed to coat an ABS (air bearing surface) of the MR head with a DLC film (diamond-like carbon film) or with a metal film such as tungsten.
However, the coating of the ABS surface with the DLC or metal film cannot perfectly prevent the MR element from being broken down due to ESD/EOS.
After the MR head is assembled into a magnetic head unit, the coating of the ABS surface of the MR head is effective for prevention of the MR element from being broken down. However, because it is not possible to prevent the MR element from being broken down at an earlier stage, this coating is done at the: final stage of the MR head manufacturing process.
Further, the coating of the ABS surface with a metal film will cause-the read output to be lower since the metal film will short-circuit the MR element.